The overall term \[Tr+1\] in the binomial development is given by \[Tr+1\text{ }=\text{ }n\text{ }C\text{ }r\text{ }an-r\text{ }br\]
Here\[n\text{ }=\text{ }12\] , \[a=\text{ }x2\] and \[b\text{ }=\text{ }-\text{ }y\text{ }x\]
Subbing the qualities we get
\[Tn+1\text{ }=12Cr\text{ }\times \text{ }x2\left( 12-r \right)\text{ }\left( -\text{ }1 \right)r\text{ }yr\text{ }xr\]
\[=\text{ }-\text{ }1r\text{ }12cr\text{ }.x24\text{ }\text{ }2r.\text{ }yr\]